Validating a website has become standard practice among designers over the last few years. As a site nears completion, the designer tests the site against the W3C Validator service to ensure that the code meets the standards, allowing them to proudly display a badge declaring their competency.
I have no real problem with this, except insofar as it provides no value (except to the designer's ego!) to show this badge.
The real problem lies with the claim that validation is inherently valuable as an SEO tactic. Sites like Google, Amazon and a plethora of other high-ranking sites stand as proof positive that validation alone will not ensure your site ranks highly.
So why is validation touted as an SEO technique?